As an imaging apparatus capable of 360° imaging, there is known an omnidirectional imaging camera used as a monitoring camera. The omnidirectional imaging camera uses a plurality of wide-angle lenses or fish-eye lenses to take images by a plurality of imaging elements, makes distortion correction and projective transform on a plurality of taken images, and combines them to produce one omnidirectional image. Images taken by adjacent imaging elements have image overlapping regions in which the images partly overlap each other. The omnidirectional imaging camera combines the images by the image overlapping regions.
The omnidirectional imaging camera takes images by using the plurality of imaging elements different in imaging direction, and the image overlapping regions of the images obtained by the imaging elements differ in brightness and color, which causes a problem of deterioration in visibility of the combined image. There has been suggested a technique for reducing differences in color tone between the image overlapping regions by correcting the image overlapping regions with the use of an initial gain for making uniform the color tones of the image overlapping regions and a correction gain for reducing differences from the other imaging elements (for example, refer to Japanese Patent No. 4739122).
The omnidirectional imaging camera takes images in a wide area using the wide-angle lenses and fish-eye lenses, and thus light from a light source such as the sun or an illumination device is likely to enter the imaging range. In this case, it is known that there is a high possibility that a flare occurs so that the images is whitely blurred and appears to have spreading of light. The flare does not occur evenly on the images, and thus the image with a flare and the image with no flare differ from each other in brightness and color. Therefore, there is a problem that a seam in the combined image is prominent.
According to the foregoing conventional technique, the differences in color tone between the image overlapping regions can be reduced to make the seam less prominent, but the other image regions cannot be corrected. As a result, the combined image has differences in brightness and color.
Therefore, there is a need to provide systems and methods allowing reduction differences in brightness and color between a plurality of images.